US 4,728,958 A · Coherent electromagnetic energy emitter locator

Abstract

An emitter location system includes a single carrier based first and second short baseline interferometers, and a long baseline interferometer operatively connected to a computing means. The computing means includes a three level processor. The short baseline interferometers provide phase measurements for level one combination into total phase measurements and estimates of the angle of incidence of the incoming electromagnetic energy. After test for acceptance, the estimated angle of incidence is passed for level two processing which includes the simultaneous processing of the estimated incident angle with the phase measurement of the long baseline interferometer for error correction to provide an improved estimated incident angle. After test for acceptance, the improved angle of incidence measurement is passed for determining the angle of the incident wave for level three processing. Level three processing utilizes the bearing estimates and the carrier position and heading information for an inertial navigation system to relate the information to a fixed coordinate system. Then the location of the emitter is determined using least square method.

Drawings

Drawings are temporarily unavailable. Open the PDF at USPTO

Drawings

Claims6

Dependent claims

An apparatus for locating emitters of electromagnetic energy comprising:

a. first and second interferometers having preselected baselines for providing phase measurements for estimating incident angle of incoming electromagnetic energy from an emitter;
b. linking means interconnecting the first and second interferometers forming a third interferometer for improving the estimates of the incident angles of incoming electromagnetic energy to provide an aliased phase measurement thereby;
c. means for providing carrier position and heading information of the apparatus;
and
d. computing means responsive to the phase measurements from the interferometers for providing estimation of the angle of incidence, for improving the estimate of the angle of incidence and for determining the bearing to the electromagnetic energy emitter and the computing means includes;
a level one data processing means operatively connected to the first and second interferometers for phase linking the phase measurements of the first and second interferometers to restore the total phase, means responsive to the total phase for estimating the angle of the incident wave, the incoming electromagnetic energy, and test means responsive to the angle of incident wave and a threshold for determining whether phase linking errors have occurred in the estimated angle and selectively passing the estimated angle to a level two data processing means for improving the estimation of the angle of the incident wave and selectively passing the improved estimated angle of the incident wave to a level three data processing means for combination with provided carrier position and heading information for determining the bearing and location of the electromagnetic energy emitter.

3 more elements

An apparatus for determining the direction and range to an electromagnetic energy emitter comprising:

(a) first and second baseline interferometers including a plurality of electromagnetic energy receivers for producing a plurality of phase measurements from incoming electromagnetic energy emanating from an emitter;
(b) a third baseline interferometer operatively connected to selected receivers of the first and second baseline interferometers for producing an aliased phase measurement;
and
(c) a computing means including first, second and third level processing means, the first level processing means operatively connected to the first and second baseline interferometers for restoring the total phase of the plurality of phase measurements received from the first and second baseline interferometers, estimating the angle of incidence from the total phase and performing a consistency test for determining whether phase linking errors have occurred and selectively passing the estimated incident angle to the second level processing means;
the second level processing means operatively connected to the first level processing means and third baseline interferometer for receiving, respectively, the incident angle estimate and aliased phase measurement and adding to the aliased measurement and integral multiple of 360 degrees for total phase restoration, storing a sequence of restored total phase measurements, constructing a temporal phase model from the sequence of restored total phase measurements and determining therefrom any phase linking errors, determining proper phase linking and passing data representing an improved incident angle, bearing estimate means responsive to the improved incident angle data for producing and passing a bearing estimate to the level three processing means;
the level three processing means operatively connected to the bearing estimate means for receiving the bearing estimates and responsive to carrier position and heading information relating the measured bearings to a fixed coordinate system, and determining the location of the emitter.

3 more elements

Dependencies are inferred from the claim text.

Description7,350 words

Summary848 words

#This invention relates to electronic reconnaissance devices and more particularly to an improved coherent electromagnetic energy emitter location device for detecting and locating radars and other electromagnetic emitters such as those in communication networks.

#The problem of locating an object on the surface of the earth by the use of indirect measurements has a long history. Surveyors and navigators, for example, have always been concerned with location estimation.

#To locate an object on the surface of the earth in a three dimensional coordinate system requires measurements on at least three independent quantities functionally related to the three coordinate values of the object. For locating electromagnetic emitters passively, the measurements generally taken are emitter altitude (from local topographic data) and either of the following: (1) direction of arrival of the electromagnetic waves at two or more locations of a single aircraft, or (2) time of arrival of emitter pulses at three aircraft locations. These measurements are then combined with the known (or estimated) locations from which they were taken, the functional relations among the various locations and measured quantities, and assumptions about the error distributions of the measurements, to arrive at an emitter location estimate.

Brief description of the drawings17 figures

#Other objects and features of the invention will become more readily understood from the following detailed description and appended claims when read in conjunction with the accompanying drawings, in which:

#FIG. 1 is an isometric view of an emitter locator system (ELS) carrier showing suitable locations for the system components;

#FIG. 2 shows the ELS components in box form;

Detailed description6,217 words

#Referring now to FIG. 1, an emitter locator system (ELS) carrier 10, which may be, for example, an airplane houses two short baseline interferometer systems 12 and 14 (FIG. 2). The short baseline interferometer systems 12 and 14, as will be hereinafter described in detail, have elements connected to a phase detector to form a long baseline interferometer system. A short baseline interferometer system is considered to have a baseline length of up to 50 wavelengths at the center frequency; a long baseline interferometer is one having a length of more than 50 wavelengths.

#The short baseline interferometer systems 12 and 14 each have receivers including an antenna and RF converter subsystem 16 and a delay line and cued analyzer 18; they share in common a channelizer 20, a frequency synthesized and local oscillator 22, a processor 24, a power supply 26 and a control panel 28.

#As shown in FIG. 1, to provide a stable baseline, the two antenna and RF converter subsystems 16 and two delay line and cued analyzers 18 are mounted in the wing nibs 30. Only one of the wing nibs is shown.

Facts

Application

06/833,937Filed 25 Feb 1986

Granted

1 Mar 1988

Term ended

25 Feb 2006

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification3 codes

G01S 5/04
Using radio waves: position of source determined by a plurality of spaced direction-finders
G01S 3/48
Using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems: the waves arriving at…
G01S
Radio direction-finding

Description7,350 words

Summary848 words

Brief description of the drawings17 figures

#FIG. 1 is an isometric view of an emitter locator system (ELS) carrier showing suitable locations for the system components;

#FIG. 2 shows the ELS components in box form;

Detailed description6,217 words

Coherent electromagnetic energy emitter locator

Life of this patent

Coherent electromagnetic energy emitter locator

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims6

Description7,350 words

Drawings

Classification3 codes

Life of this patent

Description7,350 words